Prenatal developmental toxicity studies on fumes from bitumen in the rat

Current frameworks for environmental and health assessment of hydrocarbon streams and products are flexible and ready for alternative non crude oil-based feeds

Hazard and risk assessment of complex petroleum-derived substances has been in a state of continuous improvement since the 1970s, with the development of approaches that continue to be applied and refined. Alternative feeds are defined here as those coming into a refinery or chemical plant that are not hydrocarbons from oil and gas extraction such as biologically derived oils, pyrolysis oil from biomass or other, and recycled materials. These feeds are increasingly being used for production of liquid hydrocarbon streams, and hence, there is a need to assess these alternatives, subsequent manufacturing and refining processes and end products for potential risk to humans and the environment. Here we propose a tiered, problem formulation-driven framework for assessing the safety of hydrocarbon streams and products derived from alternative feedstocks in use. The scope of this work is only focused on petrochemical safety assessment, though the principles may be applicable to other chemistries. The framework integrates combinations of analytical chemistry, in silico and in vitro tools, and targeted testing together with conservative assumptions/approaches to leverage existing health, environmental, and exposure data, where applicable. The framework enables the identification of scenarios where de novo hazard and/or exposure assessments may be needed and incorporates tiered approaches to do so. It can be applied to enable decisions efficiently and transparently and can encompass a wide range of compositional space in both feedstocks and finished products, with the objective of ensuring safety in manufacturing and use.

Developmental toxicity testing of the fume condensate extracts of bitumen and oxidized asphalt in a series of in vitro alternative assays

The potential developmental toxicity and mode-of-action of fume condensate extracts of bitumen and oxidized asphalt were evaluated in the aryl hydrocarbon receptor (AhR) CALUX assay, the zebrafish embryotoxicity test (ZET), and the mouse embryonic stem cell test (mEST). In the AhR CALUX assay, both fume condensate extracts showed a concentration-dependent AhR induction following 6-h of exposure, but this activity was substantially reduced after 24-h, indicating a transient AhR activation. The main effect observed in the ZET was early embryonic lethality that occurred mostly in the 24 h-post-fertilization (hpf). This typically reflects non-specific toxicity rather than in vitro developmental toxicity of the fume condensate extracts tested since this effect was not seen as a result of the whole cumulative exposure period in the ZET (up to 96 hpf). No malformations were seen in any zebrafish embryo exposed to these fume condensate extracts, although some developed pericardial and/or yolk-sac edemas. Furthermore, both fume condensate extracts tested negative in the mEST. In conclusion, the results show that fume condensate extracts of bitumen and oxidized asphalt do not induce any in vitro developmental toxicity, which is in line with the results observed in the in vivo prenatal developmental toxicity studies performed with the same materials.

Prenatal developmental toxicity studies on fumes from oxidised asphalt (OA) in the rat

The prenatal developmental toxicity of the fumes of oxidised asphalt (OA) was tested by nose-only inhalation in the rat. The test material was generated by collecting fumes from the headspace of storage tanks filled with OA. The composition of these fumes was matched to fumes sampled at a workplace where the same OA was applied in a pour-and-roll operation, representing occupational exposure with high concentrations of fumes to not underestimate the possible hazard. In the main study, dams were exposed to 0, 53, 158 and 536 mg/m³ of fume (as total organic mass), for 6 h/day for 19 days p.c. The maternal NOAEC was 53 mg/m³ (lowest dose tested). In the high-dose group treatment-related effects on body weight gain were seen. In the mid- and high-dose groups treatment-related effects on food consumption, lung weights, and histopathological changes in lungs and the upper respiratory tract were observed. The NOAEC for prenatal developmental toxicity was 536 mg/m³ since no exposure-related effects were found in any of the exposure groups for any of the investigated reproductive endpoints. Furthermore, nose-only exposure to OA fumes in concentrations up to 536 mg/m³ from days 1-19 p.c. did not induce any significant fetal abnormalities.